Thomas Lincoln Casey was born on May 10, 1831 at Madison Barracks, Sackett's Harbor, New York, United States. He was the eldest son of the seven children born to Brevet Major-General Silas Casey and his first wife Abby Perry (Pearce) Casey. His early ancestry was rooted in Rhode Island.
Receiving ordinary schooling in the vicinity of his birth, he was appointed, July 1, 1848, to the United States Military Academy. On July 1, 1852, he graduated first in his class and first captain of the corps and was appointed brevet second lieutenant.
Early in his career his outstanding ability brought him difficult assignments. Until 1854 he was assistant engineer for the rebuilding of Fort Delaware and improving river and harbor works in its vicinity; from 1854 to 1859 he taught engineering subjects at the Military Academy. In 1859 he went to Washington Territory and spent the next two years building a wagon road through virgin forest, the first land communication between the Columbia River and Puget Sound. He also selected and surveyed sites for military reservations along Puget Sound. When the Civil War began, Casey was made assistant engineer for the Department of Virginia. Since there was urgent need for construction of forts at key points in Maine, soon thereafter, at the age of thirty, he became superintendent of engineering to construct Fort Scammel, Fort Gorges, and Fort Preble (in Portland Harbor), Fort Popham near the mouth of the Kennebec, and Fort Knox at the narrows of the Penobscot River. Each was critically located and difficult to build. Casey himself drew most of the plans; he developed his own skilled mechanics; taught them to anchor to rock foundations half-submerged by tides; to land needed materials in nearly inaccessible places; and to build necessary derricks and other needed heavy installations. So thorough was his work that the Portland Company, builders of locomotives and marine engines, asked him to leave the army to manage their plant. Instead, he took seven months' leave of absence (July 26, 1866 - February 25, 1867), put the factory into efficient operation, and then returned to the engineer corps to take charge of all Portland harbor engineering works. In this capacity he served until November 18, 1867, when he transferred to the office of the chief of engineers, Washington, to head the division of fortifications. On March 3, 1877, as superintending engineer of public buildings, grounds, and work, Washington, he assumed supervision of construction of the State, War and Navy Building; the Washington aqueduct; and the office for public buildings and grounds. His forceful honesty and aggressive methods of execution brought startling results in the case of the State, War and Navy Building, where his system of work, his contracts for material, and his insistence upon low waste quotients saved over two and one-quarter million dollars. In 1878 the Washington Monument stood an incomplete, unlovely 173-foot pile of stone, shantyroofed. On June 25, 1878, its completion was entrusted to Casey. Originally started on a too shallow, narrow foundation, the monument, practically abandoned for twenty-three years, presented a difficult problem. In the absence of reliable recorded data, Casey devised a plan to strengthen the foundation by underpinning and buttressing with concrete, and carried the job to completion on December 6, 1884, when he personally set the cap pyramidion he had designed. He was retired on May 10, 1895. On October 2, 1888, Congress passed an act to enable completion of the Library of Congress building. Casey was given the job. He devised a simple, comprehensive plan of action, secured congressional approval, and prosecuted the work along sound engineering lines. Riding in a street car to his daily inspection of work at the Library, he was taken suddenly ill and died in a few hours.
Casey was a member of the National Academy of Sciences and an officer of the Legion of Honor of France. In 1882 he succeeded his father as a member of the Massachusetts Society of the Cincinnati. He was also a First Class Companion of the Military Order of the Loyal Legion of the United States.
On May 8, 1856, he married Emma Weir, daughter of Prof. Robert W. Weir, of the United States Military Academy. They had four sons, only two of whom survived him Thomas L. Casey, who followed his father into the engineer corps, and Edward Pearce Casey, a well-known architect.
